Hello. You did not present the experiment to which this question refers, which makes it impossible for it to be answered. However, I will try to help you in the best possible way.
It is likely that the amount of water presented in the question above is a variable in the experiment. This allows us to consider that if the experiment were carried out with different amounts of water, this experiment would provide inaccurate data and the results would not be considered true, making it impossible for a precise conclusion to be revealed.
This would happen because an experiment must distribute the variables, in all treatments, with the same amount and intensity. Therefore, to promote accurate data, the experiment must use an equal amount of water in all treatments.